Oil pump driving arrangement for a separate engine lubricating system of a small-sized internal combustion engine

ABSTRACT

A cylindrical through bore is provided in a main shaft for supporting a recoil starting device disposed at one end of a crank shaft of a two-stroke internal combustion engine. A driving shaft for an oil pump is inserted through the cylindrical through bore and drivingly and detachably coupled to one end of the crank shaft. The driving shaft is drivingly connected, through a speed reduction mechanism consisting of a worm and worm wheel, to the oil pump for a separate engine lubricating system. Each part of the speed reduction mechanism is lubricated by a supply of a lubricating oil.

United States Patent 1191 Nakamura 1 1 Dec. 31, 1974 [54] INTERNAL COMBUSTION 2,335,186 11/1943 Jackson 123/179 D ENGINE 2,887,100 5/1959 Papst 3,302,752 2/1967 Shiokawa 184/628 [75] Inventor: Toshiaki Nakamura, Hamakita, mil s: et Japan 3,585I977 6/1971 Masa0ka.... [73] Assignee: Yamaha flatsudoki Kabu hiki 3,626,937 l2/l971 Gjorik l23/l85 B Kaisha, Iwata-shi, Shizuoka-ken, J

ap-an Primary Examiner-Manuel A. Antonakas [22] Filed: Aug. 7, 1973 [21] Appl. No.: 386,375

[57] ABSTRACT 30 F'Al 't'PtD 1 A 's; y am 7 A cylindrical through bore is provided in a mam shaft Ug. 9, apan 4 for suppo ting a recoil Start ng de ice d sp e t ne endof a crank shaft of a two-stroke internal combus- [52] 123/196 123/179 g' il tion engine. A driving shaft for an oil pump is inserted 3/1 3 through the cylindrical through bore and drivingly and [5 i 1 hi. Cl- 166 l detachably coupled to one end of the crank Shaft. The [58] of Search 3 driving shaft is drivingly connected, through a speed 123/196 185 1 S reduction mechanism consisting of a worm and worm wheel, to the oil pump for a separate engine lubricating system. Each part of the speed reduction mecha- [56] References C'ted nism is lubricated by a supply of a lubricating oil.

UNITED STATES PATENTS 1,789,397 1/1931 1 5 Claims, 2 Drawing Figures Vincent 123/179 D PATENIEDUECIS 11914 sum 2 BF 2 mm Qv INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION Isage or the other necessary locations. An oil pump is controlled so that a supply of an oil is varied in connection .with the number of rotations of an engine and the operative state of the engine, for example, the degree of the opening and closing of a throttle valve, the state of a load etc.

Where an oil pump driving arrangement is applied to a small-sized internal combustion engine, a peculiar problem is presented. That is, since no sufficient space can not be taken in a crank case of theinternal combustion engine, an oil pump driving arrangement must be disposed outside of a crank case. This is an unavoidable result dueto the size, per se, of the crank case. In this case it is necessary to locate the oil pump driving arrangement, in connection with the crank shaft, on either side'of a crank shaft whose both ends extend outside of the crank case. Generally, an oil pump driving arrangement is mounted on the output side of the crank shaft. The reason for this is that it is difficult from the technical viewpoint to locate the oil pump driving arrangement on the other side of the crank shaft, since a starter device including a starter drum is mounted to the other end of the crank shaft. That is, the oil pump I belt and a split pulley sheave mounted on the output side-of the crank shaft. The oil pump driving arrangement includes gears in cooperation with the crank shaft.'With such an arrangement, however, any particular lubricating device is necessary for lubrication of the gears. It is because that, since the gear is not enclosed within the crank case, i.e., is located outside of the crank case, lubrication is not effected by a lubricating device for lubricating the interior of the crank case. For this reason it is necessary to provide a casing, separately from the crank case, for encasing the'gear so as to supply a lubricating oil or grease Thus, a high manufacturing cost of the internal combustion engine as a whole results. Besides, the crank shaft is lengthenedon the side where the oil pump driving arrangement is pro vided, and at the same time a supporting arm extending from the crank case and supporting the driving arrangement is also lengthened with the result that the rigidity and strength of the driving device can not be sufficiently held.

a speed reduction gearing mechanism including a series of gearings. As a result, the driving device as a whole is large-sized and difficulty is encountered in making the associated engine compact as well as in applying the engine to a snow mobile etc.

SUMMARY OF THE INVENTION This invention provides an oil pump driving arrangement for a conventional internal combustion engine equipped with a crank shaft, crank case, etc. With such an arrangement, a cylindrical through bore is coaxially 1 provided in a main shaft fixed to a starter housing for a starting device. A driving shaft is disposed within the through bore of the main shaft. One end of the driving shaft is drivingly and detachably coupled to one end of the crank shaft so as to drive an oil pump. The driving shaft is drivingly connected, through a speed reduction means consisting of a worm and a worm wheel, to the oil pump for a separate engine lubricating system which is outside of a crank case. A tachometer shaft adapted to drive a tachometer for measuring the rotational speed of a driving shaft, and thus a crank shaft, is drivingly connected through another speed reduction mechanism to the driving shaft. A lubricating oil is supplied by the oil pump to such part constituting said speed reduction mechanism and lubrication is smoothly effected.

One object of this invention is to provide a compact,

simplified oil pump driving arrangement having an increased rigidity and strength as a whole. I

Another object of this invention is to provide an oil pump driving arrangement capable of supplying a lubricating oil by an oil pump without the necessity of providing any particular lubricating means for lubricating the oil pump driving arrangement which is outside of a crank case. I

A further object of this invention is to provide a functionally excellent oil pump driving arrangement adapted to effect another functionutilizing a driving shaft for'an oil pumpd'riving operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view,partly broken away, to show the front section of a snow mobile equipped with an oil pump driving arrangement-accordingto this in- DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown the front portion of a snow mobile equipped with two-cycle internal combustion engine. An engine assembly 11 is generally provided with an engine cylinder, cylinder head, etc. which are disposed at the forward portion of a base frame 51 of the snow mobile. The engine assembly 11 is securely supported on the base frame 51 through a securing means such as an engine bracket 53, two band plates 54, bolts 55 and bolt and nut assemblies 56, 57. The engine assembly 11 and the front of the base frame 51 are covered by a front cowling 52.

Turning to FIG. 2, a crank shaft 12 of the engine assembly 11 is rotatably journaled, through main bearings 36, in the crank case 13. Both the ends of the crank shaft 12 extend beyond the crank case 13 and one end of the crank shaft constitutes an output taking section 12a. At the other end 12b of the crank shaft are arranged a starter device including a cup-shaped drum 14 to be described later and an oil pump driving arrangement according to this invention. At the output taking section 12a of the crank shaft 12 is provided a primary sheave 1S constituting part of a variable speed sheave drive mechanism of the snow mobile. The primary sheave 15 has a fixed sheave disk 16 secured to the output taking section 12a of the crank shaft 12, a lengthy boss section 17 formed integral with the sheave disk 16 and extending along the axis of the crank shaft 12, and a movable sheave disk 18 spline-fitted over the boss section 17 and axially slidable on the boss section 17. The movable sheave disk 18 can be rotated integrally with the boss section 17. A coil spring 19 is wound over the boss section 17 and normally urges the movable sheave disk 18 away from the fixed sheave disk 16. A sheave cap 20 is fixed to the end of the boss section 17 and holds the movable sheave disk 18, against the urging force of the spring 19, in a position remotest from the fixed sheave disk 16. In the sheave cap 20 three weights 21, only one of which is shown, are swingably supported. The weights 21 serve to cause the movable sheave disk 18 to be axially and slidably moved, against the urging force of the spring 19, from said remotest position towards the fixed sheave disk 16 in a manner to be proportional to a centrifugal force produced during the rotation of the boss section 17 and thus the sheave cap 20. Between the sheave disks 16 and 18 a V-shaped transmission belt 22 is disposed and is driven with the rotation of the disks 16, 18. The driving force of the belt 22 is imparted to a secondary sheave 58 constituting another part of the variable speed sheave drive mechanism as shown in FIG. 1. The driving speed ratio prevalent during the driving period is varied according to the variation of a relative axial distance between the sheave disks 16 and 18. The driving force imparted to the secondary sheave 58 is transmitted through the driving arrangement 59 as shown in FIG. 1 to an endless track 61 which is supportingly guided by suspension wheels 60. Thus, the track'61 is drivenv At the other end portion 12b of the crank shaft 12 a cup-shaped drum l4, cooling fan 23 and rotor 24 of a flywheel-magneto are provided. That is, the rotor 24 of the flywheel-magneto is fixed by a key 25 to the crank shaft 12. A cooling fan 23 for sending out a cooling air issecured by rivets to the rotor 24. A cup-shaped drum 14 is fixed to the fan 23 by a fastening nut 26 screwthreaded into the end portion 12b of the crank shaft.

A recoil starting device 27 is provided on the axis of the extension of the crank shaft 12. A main shaft 28 of the starting device 27 is formed in the hollow cylindrical shape and disposed to be in alignment with the axis of the crank shaft 12. At the outer periphery of the shaft 28 a starter pulley 29 is rotatably provided. The starter pulley 29 is rotated by a rope 30 wounded around the pulley, i.e., by operating a starter-knob (not shown) fitted to the end of the rope. The rotation of the pulley 29 causes pawls 31 swingably supported on the starter pulley 29 to be engaged with circumferentially spaced openings 32 formed in the cup-shaped drum 14 to permit the cup-shaped drum 14 and the crank shaft 12 to be rotated. When the starter-knob is brought back to the original position, the rope 30 is wound back to the pulley 29 to cause the pawl 31 to be disengaged from the opening 32. With such a starting device, engagement and disengagement of the pawl 31 are effected by a well known mechanism.

A flange portion 28a of the main shaft 28 is secured to a starter housing 35 which is in turn secured to a fan casing 38 by a fastening means 37 consisting of a bolt and nut. The fan casing 38 is fastened by a bolt 39 to the crank case 13. The casing 38 serves to direct a cooling air induced by a cooling fan 23 to the cylinder and cylinder head of the engine. In this way, the main shaft 28 is mounted through the starter housing 35 and fan casing 38 to the crank case 13 and held in a manner to align with the axis of the crank shaft 12.

Outside of the fan casing 38 is disposed an oil pump 40 for a separate engine lubricating system. A driving shaft 41 for driving the oil pump 40 is loosely inserted into the bore 34 of the main shaft 28 in a manner to be disposed along the axial direction. One end of the driving shaft 41 extending from the bore 34 is disposed opposite to the crank shaft 12. In the end 12b of the crank shaft 12 a round recess 42 is provided and aslit 42a is provided diametrically across the recess 42. One end of the driving shaft 41 is detachably fitted into the recess 42, and a cross pin 41a secured to the end-portion of the driving shaft 41 is driven into the slit 42a. By such detachable coupling 'means, the driving shaft 41 and crank shaft 12 are rotated as a unit and the'rotational force of the crank shaft 12 is transmitted to the driving shaft 41.

The central portion of the driving shaft 41 is located within a housing 43 integral with a fan casing 38 and the base end portion of the driving shaft 41 is passed within the casing 62 of the oil pump 40 coupled to the housing'43. The driving shaft 41 is rotatably journaled within the bearings 63 and 64 forcefully inserted into the casing. The structure and operation of the oil pump 40 is substantially the same as disclosed in N. SHI- OKAWA US. Pat. No. 3,302,752. However, the following feature will be noticed'with reference to the structure for driving'the oil pump 40. That is, on the base portion of the driving shaft 41 a worm 41c is integrally formed. In the 'oil pump40 is mounted a worm wheel 65engaged with the worm 41c. The rotation of the driving shaft 41 is transmitted to a distributor 66 through a speed reduction mechanism consisting of the worm 41 and worm wheel 65, and the distributor 66 is rotated at a slower speed than that ofthe driving shaft 41. A plunger 67 is slidably inserted into the distributor 66 and can be slided forwardly and backwardly within the distributor 66.

In this way, when a rotational force is transmitted by the driving shaft 41 to the oil pump 40, the oil pump 40 is operated. To explain the operation in a simplified manner, an oil port 66a is provided in the distributor 66. When the oil port 66a is brought, during the rotation of the distributor 66, into alignment with a suction port (not shown) provided in the casing 62, the plunger 67 is slided backwardly to cause a lubricating oil to be suctioned from an oil tank (not shown) through a suction pipe 68 into a distributor 66. On the other hand,

when the oil port 66a is brought into alignment with a discharge port (not shown) provided in the casing 62,

the plunger 67 is slided forwardly to cause the lubricating oil within the distributor 66 to be discharged through a discharge pipe 69. The discharged lubricating oil is supplied to an intake passage, etc., of the engine assembly 11. As disclosed in said US. Pat. No.

3,302,752, the sliding stroke of the plunger 67 is associated'with the operation of the engine assembly 11. A

discharge amount of oil from the oil pump 40 is proportional not only to the rotational speed of the crank shaft 12 but also to the operative state of the engine assembly 11. a

In substantially the central portion of the driving shaft 41 which confronts the housing 43, another worm 41bis provided integral with the shaft 41. The worm 41b is engaged with a worm wheel 44a secured to or integral with a tachometer shaft 44. The rotation of the driving shaft 41 is transmitted to the tachometer shaft 44 through a speed reduction mechanism consisting of the worm 41b and the worm wheel 44a. Tachometer (not shown) is connected directly, or through a tachometer cable (not shown), to the tachometer shaft 44, and the rotation speed of the crank shaft 12 is readable through the driving shaft 41 and tachometer shaft 44. Since the rotational speed of the tachometer shaft.

44 (even if a high. rotational speed of the crank shaft 12 is involved) is sufficiently diminished through said speed reduction mechanism, a general-purpose tachometer can be used.

An oil seal 45 is provided between the housing 43 and the driving shaft 41. With the housing 43 and the casing 62 sealed by the oil seal 45 is filled a lubricating oil leaked out from the oil pump 40. The oil seal 45 prevents a leakage of the lubricating oil towards the starter housing 35. The lubricating oil within the housing 43 and casing 62 allows each reduction mechanism of the worm and worm wheel for the tachometer and the oil pump to be lubricated. Reference numeral 46 shown in FIG. 2 is a cooling air inlet hole.

With the preferred embodiment of this invention the driving shaft 41 for the oil pump 40 is inserted into a hollow main shaft 28 and drivingly and detachably coupled to the'crank shaft 12. The driving shaft 41 is con nected to the oil pump 40 through a speed reduction mechanism consisting of the worm and worm wheel. From such a combined structure according to this invention the following advantages are obtained. Firstly, the rigidity and strength of the driving device is not impaired, since the crank shaft is not required to extend to an excessive extent. Secondly, asimplified structure results due to the adoption of the speed reduction mechanism consisting of the worm and worm wheel.

Thus, a simplified assembly and improved workability result in an increased production. Furthermore, it is easy to apply this apparatus to a small-sized vehicle such as a snow mobile, etc., which does not take any ample space. Thirdly, part of a lubricating oil discharged from the oil pump for the separate engine lubricating system can be utilized as a lubricant for the oil pump driving arrangement and therefore, no particular lubricating means are necessary in this respect. Moreover, as the speed reduction mechanism consisting of the worm and worm wheel is provided between the driving shaft and the tachometer, the drive shaft can be used for driving both the oil pump and the tachometer, resulting in a simplified structure and improved function. Generally, the fan casing is mounted 1. In combination with an internal combustion engine a crank case, a crank shaft rotatably supported by-and extending from the crank case through a main bearing, a recoil starter means located at one end of the crank shaft and having a starter housing'supported by the crank case, and a main shaft fixed to the starter housing and arranged coaxially on the extension of the crank shaft, the improvement comprising: an oil pump mounted on the starter housing for a separate engine lubricating system, and a driving shaft fitted through a cylindrical through bore provided in said main shaft and drivingly and detachably coupled to one end of the crank shaft so as to drive said oil pump.

2. The combination according to claim 1 wherein said driving shaft and the oil pump are drivingly connected to each other through a speed reduction means cooling fan ismounted to said one end of the crank case so as to send a cooling air towards a cylinder and cylinder head of the engine; and said recoil starter means and said oil pump are supported, through the fan casing, on the crank case.

5. In combination with a snow mobile, an internal combustion engine with;

an oil pump driving arrangement mounted, on the front portion of a frame of the snow mobile and covered with a front cowling, comprising: a crank case, a crank shaft rotatablysupported by and extending from said crank case through a main bearing, a recoil starter means located at one end of the crank shaft and having a starter housing supported by the crank case, a main shaft fixed to the starter housing in a manner to be arranged coaxially on the extension of the crank shaft, and having a cylindrical through bore coaxially therewith, an oil pump mounted on the starter housing for'a separate engine lubricating system, and a driving shaft loosely fitted through the cylindrical through bore and drivingly coupled tosaid one end of the crank shaft so as to drive said oil pump. I 

1. In combination with an internal combustion engine a crank case, a crank shaft rotatably supported by and extending from the crank case through a main bearing, a recoil starter means located at one end of the crank shaft and having a starter housing supported by the crank case, and a main shaft fixed to the starter housing and arranged coaxially on the extension of the crank shaft, the improvement comprising: an oil pump mounted on the starter housing for a separate engine lubricating system, and a driving shaft fitted through a cylindrical through bore provided in said main shaft and drivingly and detachably coupled to one end of the crank shaft so as to drive said oil pump.
 2. The combination according to claim 1 wherein said driving shaft and the oil pump are drivingly connected to each other through a speed reduction means having a worm integrally formed in the driving shaft and a worm wheel mounted on the oil pump and engaged with said worm.
 3. The combination according to claim 2 further comprising a tachometer shaft, and another speed reduction means mounted between the tachometer shaft and the driving shaft, said speed reduction means having another worm integrally formed iN the driving shaft and another worm wheel mounted on the tachometer and engaged with said another worm.
 4. The combination according to claim 1 wherein a cooling fan is mounted to said one end of the crank case so as to send a cooling air towards a cylinder and cylinder head of the engine; and said recoil starter means and said oil pump are supported, through the fan casing, on the crank case.
 5. In combination with a snow mobile, an internal combustion engine with; an oil pump driving arrangement mounted on the front portion of a frame of the snow mobile and covered with a front cowling, comprising: a crank case, a crank shaft rotatably supported by and extending from said crank case through a main bearing, a recoil starter means located at one end of the crank shaft and having a starter housing supported by the crank case, a main shaft fixed to the starter housing in a manner to be arranged coaxially on the extension of the crank shaft, and having a cylindrical through bore coaxially therewith, an oil pump mounted on the starter housing for a separate engine lubricating system, and a driving shaft loosely fitted through the cylindrical through bore and drivingly coupled to said one end of the crank shaft so as to drive said oil pump. 